Ancillary tool and method for positioning a prosthetic acetabulum of a hip prosthesis

ABSTRACT

The ancillary tool according to the invention comprises a handle for manipulating an acetabulum provided, in its distal part, with a head for gripping the acetabulum and, in its proximal part, with a surface for application of a force of impaction. The tool further comprises at least one added endpiece adapted to be removably connected to the distal end of the handle. This endpiece defines both a face for wedging the acetabulum and an opposite face for interaction of the endpiece with the head of the handle, these faces both being borne by a radially deformable supple ring. The invention is particularly applicable to the positioning of an acetabular prosthesis in an anatomical or prosthetic cavity of a patient&#39;s hip.

REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.10/758,280, filed Jan. 16, 2004, now U.S. Pat. No. 7,396,357, andentitled ANCILLARY TOOL AND METHOD FOR POSITIONING A PROSTHETICACETABULUM OF A HIP PROSTHESIS, which claims priority to France PatentApplication 03 00524 filed Jan. 17, 2003, both are hereby incorporatedby reference.

FIELD OF THE INVENTION

The present invention relates to an ancillary tool for positioning anacetabular prosthesis in an anatomical or prosthetic cavity of apatient's hip, of the type comprising a handle for manipulating theacetabulum provided, in its distal part, with a head for gripping theacetabulum and, in its proximal part, with a surface for application ofa force of impaction.

BACKGROUND OF THE INVENTION

This type of ancillary tool, commonly called “gripper/impactor tool”, isused during surgical operations for implanting a rigid acetabulum,generally made of metal, in the patient's hip. Once the acetabulum hasbeen implanted in the bone, a polymer cup is housed in the acetabulum,this cup being itself intended to receive the hemispherical head of afemoral implant or of the anatomical femur. The polymer cup is eitherconnected directly to the acetabulum, by wedging of correspondingtruncated surfaces borne by the cup and the acetabulum, or connected toa metallic shell which is received in articulated manner, substantiallyin the manner of a ball-and-socket joint, in the acetabulum fixed to thebone. A cotyloidal assembly with double mobility is spoken of in thelatter case.

A first example of this type of ancillary tool consists in a rigidhandle at the distal end of which is permanently connected a head madeof supple plastics material, such as Ertafluor (Registered Trademark).This head, whose outer dimensions are slightly greater than the innerdimensions of the acetabulum to be implanted, is introduced and wedgedin this acetabulum, allowing gripping then positioning thereof up to thelocation of impaction of the hip. However, the use of such a one-piecehead presents numerous drawbacks, as the supple material used does notallow an efficient grip if the inner dimensions of the acetabulum arenot adapted to those of the head, this often obliging the surgeon toseize the acetabulum to be implanted in one hand, in order to wedge thehead efficiently. The conditions of sterility are therefore not alwaysrespected. Moreover, the supple material of the head is often difficultto sterilize. Furthermore, once the impaction of the acetabulum iseffected, it is generally difficult to disengage the head wedged in theacetabulum.

U.S. Pat. No. 5,169,399 discloses another example of such a tool inwhich a gripper/impactor handle is adapted for positioning a prostheticassembly constituted by a metallic acetabulum and a polymeric insert,the acetabulum and the insert being positioned and impactedsimultaneously by the handle. The latter presents at its distal end asplit head whose two jaws are spaced apart from each other by acompression spring. When the surgeon brings the two jaws towards eachother by compressing the spring, the head may be introduced inside thepolymeric insert, then, by releasing one of the jaws, the prostheticassembly formed by the insert and the acetabulum retained on the insertundergoes a gripping effort by the head. This tool is complex to makeand to manipulate, the effort of grip depending directly on the force ofthe compression spring interposed between the jaws of the head.Moreover, insofar as the zone of contact between the head of the tooland the prosthetic assembly is formed by the end part of the polymericinsert of greatest diameter, the effort of impaction applied by thehandle on the prosthetic assembly cannot attain high values without riskof damage to the insert and the guiding of the acetabulum by the headduring impaction is unreliable. Under these conditions, there is noguarantee that the surgeon will not use one of his hands to hold theprosthetic assembly during grip thereof by the tool. Furthermore, thistool is not applicable to the positioning of a cotyloidal assembly withdouble mobility set forth hereinabove, the grip of the insert notensuring hold of the acetabulum to be implanted.

Document WO 95/11641 discloses another tool of the afore-mentioned type,which further comprises a metallic endpiece removably added to thedistal end of the handle for manipulating the acetabulum to beimplanted. A deformable member of the endpiece is constituted by fourquadrants, namely two diametrically opposite rigid quadrants fixedlyconnected to a proximal part of the endpiece by bridges of matter, andtwo diametrically opposite mobile quadrants, each connected to one ofthe rigid quadrants by an elastically deformable hinge. Pivoting of thetwo mobile quadrants is controlled by screwing the handle in theproximal part of the endpiece. However, the use of these two mobilequadrants ensures an efficient wedging of the acetabulum only in twodiametrically opposite zones of its inner face, in other words only witha limited gripping force.

It is an object of the present invention to propose a tool which isadapted to acetabula of different dimensions and nature and whichensures both an efficient grip of the acetabulum and a good applicationof the force of impaction, without hindering the withdrawal of the toolonce positioning has been effected.

SUMMARY OF THE INVENTION

To that end, the invention relates to an ancillary tool for positioningan acetabular prosthesis in an anatomical or prosthetic cavity of apatient's hip comprising a handle for manipulating the acetabulumprovided, in its distal part, with a head for gripping the acetabulumand, in its proximal part, with a surface for application of a force ofimpaction, and at least one added endpiece adapted to be removablyconnected to the distal end of the handle and defining both a face forwedging the acetabulum and an opposite face for interaction of theendpiece with the head of the handle, wherein the endpiece comprises asupple ring radially deformable with respect to the longitudinal axis ofthe endpiece, on which are formed the wedging and interaction faces.

The use of the radially deformable ring makes it possible both toguarantee an efficient grip, the surgeon being able to control hold ofthe endpiece by the head of the handle, and to efficiently transmit atleast a part of the effort of impaction up to the acetabulum. By havingavailable a series of endpieces of different sizes, the surgeon is ableto use the same manipulation handle for positioning acetabula ofdifferent dimensions and/or nature.

According to other characteristics of this ancillary tool, takenseparately or in all technically possible combinations:

the ring is radially deformable over substantially the whole of itsperiphery;

the face of the endpiece intended for wedging the acetabulum isconstituted by substantially the whole outer face of the ring;

the endpiece comprises both a supple part including the deformable ringand a rigid part fast with the supple part and provided with means forremovable connection to the distal end of the handle;

the rigid part of the endpiece is constituted by a metallic insert fixedto the supple part;

the deformable ring is elastically connected to a base of the supplepart;

the deformable ring comprises a plurality of petals, the wedging andinteraction faces being respectively constituted by the outer and innersurfaces of each of these petals;

the rigid part of the endpiece defines a stop surface, in thelongitudinal direction of the handle, for the head of the handle;

the supple part of the endpiece presents at least one surface fortransmission of the force of impaction between the handle and theacetabulum;

the head of the handle defines a ramp surface adapted to cooperate withthe interaction face of the endpiece;

the handle comprises a rigid rod on which the head is movably mounted,as well as means for driving the head with respect to the rod in amovement of translation in the longitudinal direction of the rod;

the handle comprises a sleeve disposed coaxially to the rod and at thedistal end of which the head is rigidly fixed and the means for drivingthe head with respect to the rod comprise a grip screwed on the rod andconnected in translation with the sleeve, this sleeve being immobilizedin rotation with respect to the rod; and

a ring is axially interposed between the sleeve and the screwed grip.

The invention also relates to a method for positioning an acetabularprosthesis in an anatomical or prosthetic cavity of a patient's hip,comprising the steps of:

using, on the one hand, a handle for manipulating the acetabulum,provided, in its distal part, with a head for gripping the acetabulumand, at its proximal end, with a surface for application of a force ofimpaction, and, on the other hand, a series of endpieces of differentdimensions and/or geometry, each comprising a supple ring radiallydeformable with respect to the longitudinal axis of the endpiece, onwhich are formed both a face for wedging the acetabulum and an oppositeface for interaction of the endpiece with the head of the handle;

selecting, from the series of endpieces, an endpiece of which thewedging face is substantially complementary of the inner wall of theacetabulum to be positioned;

connecting the endpiece to the distal end of the handle;

placing the endpiece in the acetabulum;

placing the endpiece in engagement by the head of the handle so as toprovoke radial deformation of the ring and consequently grip of theacetabulum by the endpiece;

positioning the acetabulum in the cavity of the patient's hip;

applying a force of impaction on the corresponding surface of thehandle;

disengaging the head from the endpiece; and

withdrawing the endpiece from the positioned acetabulum.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more readily understood on reading the followingdescription given solely by way of example and with reference to theaccompanying drawings, in which:

FIG. 1 is an exploded view in perspective of an ancillary tool accordingto the invention, and of an acetabular prosthesis.

FIG. 2 is a longitudinal section through the tool of FIG. 1.

FIG. 3 is a view of detail III in FIG. 2.

FIG. 4 is a longitudinal section of a variant endpiece of the tool ofFIG. 1.

FIG. 5 is a longitudinal section of a part of the tool provided with theendpiece of FIG. 4, and

FIG. 6 is a longitudinal section through a variant of a tool accordingto the invention.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to the drawings, and firstly to FIGS. 1 to 3, an ancillarytool 1 for positioning a metallic acetabular prosthesis 2 is shown. Thistool essentially comprises a handle 4 extending about an axis X-X and anadded endpiece 6 adapted to be removably connected to the distal end ofthe handle. The acetabulum 2 comprises a substantially hemisphericalinner wall 2 a and is intended to form, with an internal shell (notshown), a cotyloidal assembly with double mobility as set forthhereinbefore.

The handle 4 comprises a rigid rod 10 at the proximal end of which isrigidly fixed a knob 12. This knob presents a slightly convex proximalsurface 14, forming a surface for application of a force of impaction.

Passing from the proximal end of the rod 10 towards its distal end, therod comprises a first cylindrical section 15 on which is fixedly added aknob 16 for manipulation, connected to the rod by, for example, atapered pin 18. The rod then comprises a threaded section 20 of diameterlarger than the section 15, then a smooth section 22 of smaller diameterand on the outer surface of which is formed a longitudinal groove 24.The distal end of the rod is formed by a projecting catch 28 coaxial tothe axis X-X and threaded.

The handle 4 also comprises a tubular sleeve 32 mobile with respect tothe rod 10 and arranged coaxially to sections 20 and 22. This sleeve isprovided at its distal end with a head 34 whose outer shape is truncatedand convergent towards the distal end of the handle. Consequently thishead defines a truncated ramp surface 36 as well as a substantiallyplanar distal surface 38.

The proximal end of the sleeve 32 forms a substantially cylindrical foot40 from which a projecting end flange 42 extends radially.

The foot 40 is provided with a cylindrical pin 44 which extends inside asubstantially complementary recess formed in a direction radial withrespect to axis X-X. The length of this pin is greater than thethickness of the foot, with the result that a part of the pin extendsinside the sleeve 32 and is engaged in the longitudinal groove 24 of therod 10. The sleeve 32 is thus immobilized in rotation with respect tothe rod, but free to move in a movement of translation in the directionX-X.

The ancillary tool 1 comprises means for driving the sleeve 32 intranslation with respect to the rod 10, these means being in the form ofa tubular body 46 of generally cylindrical shape and essentiallydisposed coaxially with respect to the threaded section 20. Internally,the body 46 defines a tapping 48 complementary of the section 20 of therod 10. At its distal end, the body 46 is provided with twodiametrically opposite re-entrant flanges 50 spaced apart from eachother by a distance greater than the outer diameter of the end flange 42of the sleeve 32. Consequently, these flanges 50 form for the sleeve 32hooks for drive in direction X-X. Externally, the body 46 presents flatportions 52 ensuring correct grip of the body with a view to urging itin a movement of rotation about its axis.

A ring 54, made of synthetic material, for example polyacetal, isaxially interposed between the sleeve 32 and the tubular body 46. Moreprecisely, this ring comprises a cylindrical body 56 presenting an outerthread complementary of the thread of the tapping 48, and an annularskirt 58 of outer diameter greater than the diameter of the recess 48.The skirt 58 forms a protective layer for the sleeve 32 when the rod 10,and therefore the body 46 screwed on this rod, is under stress, byapplication of a force of impaction on the knob 12.

As for the endpiece 6, it extends about an axis Y-Y, coaxial to axis X-Xin FIG. 2. It is formed by a supple body 60, constituted for example bypolyacetal, and by a metallic insert 62 connected to the body 60 by, forexample, a pin 88.

More precisely, the body 60 comprises a hemispherical base 64 whoseouter shape is substantially complementary of the inner wall 2 a of theacetabulum 2, as well as a ring 66 of petals 68 connected to the base 64by elastically deformable connecting zones 70. By simultaneousdeformation of these zones 70, the ring 66 presents a considerablecapacity of radial deformation with respect to axis Y-Y. In other words,the ring 66 is radially deformable over substantially the whole of itsperiphery, the petals 68 being able to move apart radially inhomogeneous manner.

To that end, the ring 66 defines a face 72 for wedging the acetabulum 2,constituted by the outer surfaces 74 substantially in the form ofspherical frustum of each of the petals 68, and a face 76 forinteraction of the endpiece 6 with the head 34 of the sleeve 32,constituted by the inner surfaces 78 of the petals 68 which formcounter-ramp surfaces for the ramp surface 36 of the head 34. Each innersurface 78 comprises a cylindrical part extended rearwardly by a flaredpart convergent towards the base 64.

The metallic insert 62 is formed by a cylinder 80 from which a flange 82extends radially at one of its ends. The cylinder 80 is screwed in thebase 64 of the body 60 and forms a tapping 84 complementary of theprojecting catch 28 fast with the rod 10. The flange 82 forms a stopsurface 86 for the planar surface 38 of the head 34.

The ancillary tool 1 is used as follows.

Considering the handle 4 in the mounted state as shown in FIG. 2, thesurgeon introduces the distal end of the rod 10 in the endpiece 6,rendering axes X-X and Y-Y coaxial. The endpiece 6 is connected to thehandle 4 by screwing the catch 28 in the tapping 84 of the insert 62.The surgeon then grips the tool in one hand at the level of themanipulation knob 16 and in the other hand at the level of the body 46forming grip, and rotates the grip 46 with respect to the rod 10 inclockwise direction, observing the body from its proximal end. In themanner of a screw-nut system, the grip 46 pushes the sleeve 32 in amovement of translation along axis X-X, taking the head 34 inside thering 66 of the endpiece. By continuing this drive movement, the rampsurface 36 cooperates with the counter-ramp surfaces 78 borne internallyby the petals 68 so as to radially expand the ring 66 and thus apply theouter surfaces 74 of the petals against the inner wall of the acetabulum2. In other words, the ring 66 passes from a configuration of rest to anoutwardly expanded configuration, of which the substantially circularouter contour presents a diameter greater than that of the contour ofthe ring in its configuration of rest. It will be understood that thewhole outer face 74 of the ring 66 then participates in the wedging ofthe acetabulum 2. In this respect it will be noted that, for the tool 1shown, the petals 68 of this ring are identical, which does not limitthe invention in that the radial deformation of the ring by the head ofthe tool must be provided in particular to bring about the virtuallysimultaneous abutment of the essential of the outer surface of the ringon the inner concave face of the acetabulum to be manipulated.

The surgeon continues this movement until he considers that the endpieceis sufficiently retained by the head to guarantee a correct grip of theacetabulum by the endpiece by wedging. The stop surface 86 borne by theendpiece avoids any risk of excessive deformation of the petals, theinsert 62 thus imposing a maximum axial position for the head 34.

The surgeon then manipulates the acetabulum freely with the aid of theancillary tool 1, positions it on the patient's hip at the level of ananatomical cavity or a prosthetic one, i.e. formed by a previouslyimplanted bone-reconstructing plate. Then, with the aid of a suitablehammer, he applies a force of impaction on the surface 14. The effort ofimpaction is transmitted in the direction X-X of rod 10 to the rigidinsert 62 which is screwed on this rod, then from the insert to the base64 of the supple body 62, and finally from this base to the acetabulum 2through the outer surface 64 a of the base, causing the acetabulum to beforce-fitted in the corresponding cavity of the hip.

Once the impaction is effected, the surgeon rotates the grip 46 withrespect to the rod 10 in anti-clockwise direction so as to disengage thehead 34 from the endpiece 6. By elastic return deformation of theconnecting zones 70, the petals 68 resume their initial position, makingit possible to withdraw the endpiece from the implanted acetabulumwithout effort.

The ancillary tool according to the invention thus makes it possibleeasily to manipulate an acetabular prosthesis to be implanted, and withprecision. The surgeon is at no moment obliged to touch the acetabulumwith his hands. The effort of impaction is efficiently transmitted tothe acetabulum, in the longitudinal direction of the handle 4, and thisthrough the supple part of the endpiece. The risks of marking, and evendamaging the impacted acetabulum are thus limited, unlike the impactortools disclosed in the prior art, such as those envisaged in U.S. Pat.No. 5,169,399 and WO-95/11641 mentioned hereinbefore, for which hardparts of the tools are applied directly on the edge of the acetabulum,in other words at the level of a fragile zone of restricted area.

The ancillary tool according to the invention advantageously comprises aseries of endpieces whose dimensions and geometries are different. Forexample, this series comprises, in addition to endpiece 6, an endpiece6′ shown in FIG. 4, having the same general structure as the endpiece 6,but of which the outer face of the supple body is formed for anacetabulum whose inner wall is partly truncated. This endpiece isadapted for the grip and impaction of acetabula in which a polymericinsert is directly connected by wedging.

More precisely, the endpiece 6′ is essentially constituted by the sameelements as the endpiece 6, these latter having the same referencefigures to which a prime is added. In this way, endpiece 6′ comprises abody 60′ of supple material and a rigid insert 62′, rigidly fixed toeach other by a screw 88′. Apart from the geometry of its outer face,endpiece 6′ of axis Y′-Y′ differs essentially from endpiece 6 by theshape of its petals 68′ and the zones 70′ for connection with the base64′; the outer face 74′ of each petal 68′ is truncated, convergenttowards the base, the inner face 78′ of each petal is flared over thewhole of its length and the connection zones 70′ extend parallel to axisY′-Y′.

As shown in FIG. 5, the head 34 of the handle 4 is then equipped with abush 90 connected to the rest of the sleeve 32 by a retaining clip 92.This bush increases the outer dimension of the head 34 so as to adaptthe latter to the endpiece 6′ and thus laterally defines a ramp surfaceadapted to cooperate with the interaction face 76′ of the endpiece.

The use of the ancillary tool 1 provided with the endpiece 6′ issubstantially similar to the use described previously. During theapplication of the effort of impaction, the force is essentiallytransmitted to the acetabulum by the truncated surfaces 74′ of thepetals 68′.

FIG. 6 shows a variant of the ancillary tool 1 which essentially differsfrom the tool of FIGS. 1 to 3 by the following:

Contrarily to the manipulation handle 16 of the preceding Figures, whichis rigidly connected to the rod 10, the ancillary tool of FIG. 6comprises a manipulation handle 100 which is connected to the grip 46screwed on the rod 10. The use of this variant is substantially similarto that of the tool of FIGS. 1 to 3, the user having, in order toprovoke the displacement of the head 34 in translation with respect tothe rod 10, to apply a movement of rotation on the grip 46/handle 100assembly, for example by gripping the handle 100 in one hand and theknob 12 with the other hand.

Various arrangements and variants of the ancillary tool according to theinvention may also be envisaged:

materials other than polyacetal may be used for making the supple bodyof the endpiece 6, the materials retained having both to combine a goodshock resistance by reason of the transmission of the efforts ofimpaction, and a good resistance to sterilization, and not to damage theinner wall of the acetabulum to be implanted; and/or

the endpiece added to the distal end of the handle of the ancillary toolis formed in one piece, for example of synthetic material, formed by asupple part comprising a ring which is radially deformable inhomogeneous manner, similar to ring 66, and by a more rigid part, forexample of reinforced material, in which the handle is removablyconnectable.

The invention is further set forth in the claims listed below. Thisinvention may take on various modifications and alterations withoutdeparting from the spirit and scope thereof. In describing embodimentsof the invention, specific terminology is used for the sake of clarity.The invention, however, is not intended to be limited to the specificterms so selected, and it is to be understood that each term so selectedincludes all technical equivalents that operate similarly.

The invention claimed is:
 1. An ancillary tool for positioning andseating a prosthetic acetabulum in an anatomical or prosthetic cavity ofa patient's hip, the tool comprising an endpiece and a handle adapted tomanipulate the acetabulum, the endpiece comprising an elasticallydeformable ring including a plurality of petals, the handle including arod and a head, the tool having a first configuration in which the headis coupled with the rod and disengaged from the elastically deformablering permitting the petals to elastically contract with respect to alongitudinal axis of said endpiece and a second configuration in whichthe head is coupled with the rod and is received in the elasticallydeformable ring, the petals of the elastically deformable ring includingouter surfaces adapted to wedge against the inner surface of theacetabulum and opposite inner surfaces adapted to interact said endpiecewith said handle when the tool is in the second configuration, whereinsaid endpiece includes a supple part and a rigid part secured to thesupple part, wherein the rigid part includes structure for removablysecuring the rod to the endpiece and wherein said handle furtherincludes elements for applying a first force to urge said head intocooperative engagement with said inner surfaces of said petals of theelastically deformable ring in the second configuration to therebyradially expand said petals of the elastically deformable ring withrespect to the longitudinal axis of said endpiece, wherein said elementsinclude a threaded portion on the rod, a grip screwed on the threadedportion and a movable sleeve fitted between the grip and the head. 2.The ancillary tool of claim 1, wherein the grip is adapted tolongitudinally move the sleeve with respect to the rod to engage theendpiece and wherein the sleeve is adapted to impart the first forcewhen the grip is rotated to move the sleeve into engagement with theendpiece.
 3. The ancillary tool of claim 1, wherein the rigid part ofthe endpiece includes a tapped section adapted to be secured to athreaded section on a distal end of the rod.
 4. The ancillary tool ofclaim 3, wherein the endpiece is secured to the rod by screwing thethreaded section on the distal end of the rod into the tapped section ofthe rigid part of the endpiece.
 5. The ancillary tool of claim 1,wherein the tool includes a knob fixed to a proximal end of the tool. 6.The ancillary tool of claim 5, wherein the tool is adapted to transmitan impact force imparted on the knob to the proximal end of the tool. 7.The ancillary tool of claim 1, wherein the elastically deformable ringis elastic such that the ring expands from the first configuration tothe second configuration with the application of the first force andcontracts substantially to the first configuration when the first forceis removed.
 8. The ancillary tool of claim 1, wherein the petals areadapted to move apart radially in a homogenous manner when contacted bythe head.
 9. The ancillary tool of claim 1, wherein the outer surfacesof the petals of the elastically deformable ring are further adapted towedge against the inner surface of the acetabulum without damaging theinner surface of the acetabulum.
 10. The ancillary tool of claim 1,wherein the elastically deformable ring comprises an outer shape that issubstantially complementary to the inner surface of the acetabulum. 11.The ancillary tool of claim 1, wherein an outer surface of theelastically deformable ring is configured to not damage the inner wallof the acetabulum when the outer surface participates in wedging of theinner wall of the acetabulum.
 12. An ancillary tool for positioning andseating a prosthetic acetabulum in an anatomical or prosthetic cavity ofa patient's hip, the tool comprising a handle that includes a rod havinga threaded medial portion and a threaded distal portion, a movablesleeve non-rotatably coupled to the rod to move in distal and proximaldirections on the rod, a grip adapted to rotate on the threaded medialportion of the rod to move the sleeve, a movable head adapted to move indistal and proximal direction on the rod and engages an endpiece, theendpiece having an elastically deformable ring including a plurality ofpetals mounted on a rigid part that contains a threaded portion tosecure the endpiece to the rod, wherein the petals have outer surfacesadapted to engage the inner surface of a prosthetic acetabulum when thehead is forced on inner surfaces of the petals.
 13. The ancillary toolof claim 12, wherein the grip is adapted to longitudinally move thesleeve and the movable head into contact with the endpiece to radiallyexpand the petals from a first configuration to a second configurationand secure the endpiece in the prosthetic acetabulum by gripping theinner surface of the prosthetic acetabulum with the outer surfaces ofthe petals.
 14. The ancillary tool of claim 12, wherein the petals areconnected to the rigid part of the endpiece by elastically deformableconnecting zones.
 15. The ancillary tool of claim 12, wherein the petalsare adapted to move apart radially in a homogenous manner when contactedby the head.
 16. The ancillary tool of claim 12, wherein the petals moveradially in order to contact the inner surface of the acetabulum. 17.The ancillary tool of claim 12, wherein the tool includes a knob fixedto a proximal end of the tool.
 18. The ancillary tool of claim 17,wherein the tool is adapted to transmit an impact force imparted on theknob to the proximal end of the tool.
 19. The ancillary tool of claim 9,wherein the elastically deformable ring is elastic such that the ringexpands from a first configuration to a second configuration when thehead engages the ring and contracts substantially to the firstconfiguration when the first force is removed.
 20. An ancillary tool kitfor positioning and seating a prosthetic acetabulum in an anatomical orprosthetic cavity of a patient's hip, the kit comprising: a plurality ofendpieces, each endpiece having an elastically deformable ring includinga plurality of petals mounted on a rigid part, the rigid part containinga threaded portion and a stop surface; and a tool comprising a handlethat includes a rod having a threaded medial portion and a threadeddistal portion, a movable sleeve adapted to move in distal and proximaldirections on the rod, a grip adapted to rotate on the threaded medialportion of the rod to move the sleeve, a movable head adapted to move indistal and proximal direction on the rod and to engage one of theplurality of endpieces, the threaded portion of the rigid part of theendpieces adapted to secure the endpieces to the threaded distal portionof the rod, the stop surface of the rigid part of the endpieces adaptedto abut the moveable head when the moveable head is fully advancedrelative to one of the endpieces, wherein the petals have outer surfacesadapted to engage the inner surface of a prosthetic acetabulum when thehead is forced on inner surfaces of the petals.
 21. The ancillary toolkit of claim 20, wherein the plurality of endpieces includes endpiecesthat vary in size in order to accommodate a variety of different sizedprosthetic acetabulum.
 22. An Ancillary tool for implanting a prostheticacetabular cup into an anatomical cavity or hip prosthesis of a patient,comprising a handle for manipulating the acetabular cup, which in itsdistal part is provided with a head for gripping the acetabular cup andin its proximal part is provided with a surface for applying animpaction force, and at least one cap is applied, which is adapted to beinterlocked in a removable way with the distal end of the handle,defining at the same time a face for wedging the acetabular cup and anopposite face for the cap to interact with the head of the handle,wherein the cap has a base and a crown, which crown is connectedelastically to the base so that it may be distorted radially in relationto the longitudinal axis of the cap and comprises several lobes, thefaces for wedging and interacting being made up respectively of theexternal surfaces and internal surfaces of each of these lobes; whereinthe tool has a first configuration in which the head is interlocked withthe distal end of the handle and the crown is radially contracted towardthe longitudinal axis of the cap and a second configuration in which thehead is interlocked with the distal end of the handle and is disposed inthe crown and radially distorts the crown away from the longitudinalaxis.
 23. The ancillary according to claim 22, wherein the crown isconnected elastically to the base so that it may be distorted radiallyover more or less the whole periphery of the crown.
 24. The ancillaryaccording to claim 22, wherein the cap comprises at the same time afirst part, including the base and the crown, and a second part, whichis more rigid than the first part, interlocking with the first part andprovided with means of interlocking in a removable way at the distal endof the handle.
 25. The ancillary according to claim 24, wherein thesecond part of the cap is made up of a metal insert, which is fixed tothe first part.
 26. The ancillary according to claim 24, wherein thesecond part of the cap delimits a stopping surface for the head of thehandle in the longitudinal direction of the handle.
 27. The ancillaryaccording to claim 24, wherein the first part of the cap has at leastone surface for transmitting the impaction force between the handle andthe acetabular cup.
 28. The ancillary according to claim 22, wherein thehead of the handle defines an inclined surface, which is adapted tocooperate with the face for interacting with the cap.
 29. The ancillaryaccording to claim 22, wherein the handle comprises a rigid rod, onwhich the head is fitted in a moveable way, as well as means ofentrainment of the head in relation to the rod in a translatory movementin the longitudinal direction of the rod.
 30. The ancillary according toclaim 29, wherein the handle comprises a sleeve, which is arrangedcoaxially to the rod, at the distal end of which the head is fixedrigidly, and in that the means of entrainment of the head in relation tothe rod comprise a handgrip, which is screwed onto the rod and connectedin translation with the sleeve, this sleeve being immobilised inrotation in relation to the rod.
 31. The ancillary according to claim30, wherein a ring is interposed axially between the sleeve and thehandgrip, which is screwed on.